This invention relates to a circuit arrangement in which a capacitor unit suitable for a.c. operation is connected in series with an a.c. power load.
Circuit arrangements of this type are generally known as starting circuits for single-phase induction motors. As a rule, polarized electrolytic capacitors are used as starting capacitors, because such capacitors are low in price and can be operated for brief periods with alternating current.
In order to extend the life of these electrolytic capacitors, it is proposed in German Offenlegungsschrift 32 06 187 that the capacitors be switched off as quickly as possible after the motor has been started. In this manner, the capacitors are subjected to a load for only a brief time and is thus protected. Such prompt removal of the capacitors from the circuit after the switching on a single-phase induction motor may, however, have detrimental consequences for the motor. The removal of the starting capacitor reduces the starting torque so that the run-up of the motor will take a longer time, with the result that the motor winding experiences intense heating. Furthermore, disturbances during run-up may occur if the motor is subjected to a varying load.